Method and device for ensuring reliability during transmission of television data in a television system based on internet protocol

ABSTRACT

A coding/transmitter device ( 11 ) includes a broadcasting module ( 12 ) in order to broadcast television to a plurality of STB receiver/decoder devices ( 15 ) via an IP/Internet network ( 14 ), so that the clients-subscribers are provided with a first UDP stream and a second UDP stream which includes identification data associated with data packets transmitted within the first UDP stream in order to provide functionalities such as reorganisation of packets, detection of losses, requests for retransmission etc. without adding headers according to the RTP protocol, but with a reliability and capability of inserting additional data comparable to that provided by the RTP protocol.

OBJECT OF THE INVENTION

The present invention refers in general, to Internet Protocoltelevision, IPTV and in particular, to a method and device fortransmitting multimedia television content from a digital televisionplafform to a plurality of clients through a telecommunications network,such as a network based on Internet protocol, Internet/IP protocol.

STATE OF THE ART

The broadcasting of television and video signals on demand from an IPnetwork on broadband connections is becoming increasingly common. InIPTV a number of digital television services are supplied to consumerswho use IP Protocol, being typically supplied by a broad band operatorwhich uses the Internet/IP network infrastructure.

IPTV covers both active television in multicasting as well as video ondemand, or VOD. IPTV requires a decoder device for subscribers or atelevision decoder interface, that is, a set top box or STB, connectedto a television screen.

The multimedia content received for decoding and showing on screen maybe supplied through multicasting (IP), where the information istransmitted simultaneously to the group of receivers/decoders or STBinterface.

Generally, in a multicast IPTV system the user datagram protocol or UDPis used, without connection, as it is fast and because the packets withUDP format include a reduced packet header compared to a transmissioncontrol protocol or TCP header.

In the UDP protocol datagrams are generated which are transmittedaccording to the IP protocol which defines a packet switching networkand which links the different operator devices with the subscribers' STBinterfaces. Each packet is transmitted with the STB interface addresswhere it is to be received or with a multicasting address and eachpacket is transmitted independently from the others through the IPnetwork until it reaches its destination.

The TCP format provides a reliable transport service for packets as forexample; it also retransmits any lost data packets.

For this purpose, the TCP protocol fragments the information andtransmits and numbers each packet, that is, it assigns an identificationlabel so that the receiver of the packet stream can order them onreceipt should they arrive in a disordered form or if any packet doesnot reach its destination.

However, the UDP protocol does not provide guarantees of reliabletransmission of information provided by the TCP protocol, therefore, itdoes not verify that the packets reach their destination, and thus itdoes not provide guarantees that they will arrive in order, that all thepackets are received, or that there are no errors in the information incontains. In the latter case, the packet involved is set aside in thenetwork layer and is not delivered to the application layer.

The UDP protocol does not have the means to remedy possible deficienciesmentioned previously as the overload of headers, retransmissions andtwo-way communications which provide reliability, packets in TCP format,are disproportioned for the flow of multimedia data.

A disadvantage of the TCP header is that it introduces delays in thetransmission which are not assumable in IPTV.

Therefore, the UDP protocol is used normally for multimedia streamingapplications (audio, video etc) where the prompt arrival of the packetsis more important than the reliability provided by information, so thatthe receiver communicates the success or failure of the transmissioninformation which identifies the packet received and information fromthe previous and subsequent packet, in order to maintain the order ofthe packets sent.

The multimedia transmissions specify that the STB interface receivepackets in real time. However, there are STB interfaces which are notable to detect and act in the event of loss, disorder and corruption ofdata packets.

Consequently, if during transmission of data packets according to theUDP protocol, any error occurs, the STB interface is unable to notifyany event during reception of the packets and acts in consequence forexample, requesting the resending the packets involved.

Moreover, the UDP protocol has no means of inserting additional dataassociated with the video, as its payload is a bare sequence of videolayer packets such a sequence of MPEG2 Transport Stream packets.

As a remedy for some of the problems described above the RTP protocolhas been designed to add a header to the UDP format, containinginformation to identify the packet received and, therefore, usable withdata packets in real time such as multimedia audio and video streamingwhich is mounted on UDP format.

The RTP protocol in addition permits additional information to betransmitted, associated with the audio and video flow which enablesadded value services to be implemented, such as rapid changing ofchannel, recovery in the event of FEC (Forward Error Correction), datasynchronised with the video, etc.

It should be noted that a number of STB interfaces are installed whichare able to extract information contained in RTP format headers.

It should however be noted as well that many legacy STB interfacescurrently installed are not able to understand the RTP protocol formatand cannot work at all with multimedia streams encapsulated in RTP. Ifthe multimedia stream is exclusively encapsulated with RTP protocol,these legacy STB interfaces will stop working.

The generation and insertion of RTP headers in the main multimedia flowrequires in general a major change in the main path of the multimediastream, including the replacement of updating of the devices in chargeof encapsulating the MPEG2 Transport Stream packets at the Headend

CHARACTERISATION OF THE INVENTION

This invention seeks to resolve or reduce one or more of thedisadvantages mentioned above by means of a method and a device forensuring reliability during transmission of digital television datastreams on Internet protocol and inserting additional informationassociated to video for enabling added value services according to Claim1. Embodiments of the invention are established in the dependent claims.

One object of the invention is to provide a method and system fortransmitting television data streams, according to the UDP protocol viaan internet protocol telecommunications network, in a manner that doesrequire a change in the current format of the main video stream andtherefore does not interfere with the operation of legacy STB interfaceswhich are installed in the field

Another object of the invention is to send additional informationassociated to the video data through a separate stream that can followan independent path and can therefore be handled independently by thenetwork equipment and even be filtered out at certain locations ifdesired

Yet another object of the invention is to generate the stream with theadditional information using a separate device at the Headend which doesnot interfere with the main UDP stream and therefore does not requireany changes in the currently installed encapsulators.

Another object of the invention is to enable the deployment of the addedvalue services in a gradual manner in space and time

BRIEF DESCRIPTION OF THE FIGURES

A more detailed explanation of the invention is given in the followingdescription based on the attached figures in which:

FIG. 1 shows a block diagram of a system for television transmission inaccordance with the invention.

DESCRIPTION OF THE INVENTION

In relation to FIG. 1, the method of the invention permits transmissionin broadcast and unicast data streams relating to multimedia containedaccording to UDP protocol via a telecommunications 14 network such as anInternet/IP network in a reliable manner, ensuring high reliability ofthe multimedia signal transmitted and including information whichenables added value services.

The method is applicable to data streams based on conventional UDPprotocols, thus interoperability with coding/transmitter 11 devices ofexisting content suppliers is maintained.

The UDP television data stream generated may be a data stream forextensive multicasting.

A coding/transmission 11 device, belonging to a multimedia contentsupplier, including a broadcast 12 module for broadcasting television toa plurality of receiver/decoder 15 devices or set top box STB televisiondecoder interfaces, associated with subscribers via the IP network 14,so that the customers-subscribers are provided with broadcastingservices in which MPEG-2 transport stream packets are transmitted inmulticast, unicast or broadcast using UDP protocol, without addingheaders according to RTP protocol, however with a reliability andcapability of sending additional information comparable to that providedby the RTP protocol, as will be shown hereafter.

The broadcasting module 12 compresses and encapsulates the contents tobe transmitted, MPEG streams in standard UDP format, generating in oneof its outlets a first UDP packet stream and transmitting it to the STBinterfaces 15 of the subscriber side of the IP network 14.

Furthermore, the coder/transmitter device 11 includes a firstfingerprinting module 13 which receives the first UDP stream generatedby the broadcasting module 12, reads it, generates a packetidentification data applying a fingerprinting technique on each packetof the first UDP stream, encapsulates this identification data with someadditional information associated to the packet and transmits it on asecond UDP data stream via one of its outlets.

The second UDP data stream is transmitted on a second communicationschannel different from a first communications channel on which the firstUDP stream is transmitted to the group of STB interfaces 15.

The fingerprinting technique enables a series of associatedidentification parameters to be obtained in order to form a fingerprintwhich unequivocally identifies each UDP packet of the first UDP datastream.

Therefore, the fingerprinter module 13 generates with the identificationdata associated to each UDP packet of the first UDP stream plus theadditional information associated to it a second UDP data stream.

It should be noted that the second UDP data stream includesidentification data of packets associated with the packets transportedwithin the first UDP transport stream, together with informationassociated with that identification data, which is equivalent to theinformation carried by other protocols such as RTP.

From the coding/receiver device 11 both first and second UDP streams aretransmitted on parallel canals to the subscriber side, being received bythe receiver module of the STB interface 15.

The receiver module 16 receives the first UDP stream and redirects it toa decoding module of the STB interface 15, so that it may be decoded andthe decoded outlet signal is retransmitted to the television screen forviewing of the multimedia signal received, in exactly the same way as itis done by all currently installed legacy STB interfaces.

The receiver module 16 also receives the second UDP stream and itredirects it to a second digital fingerprint module 17, which extractsfrom the second UDP stream the identification data, expected fingerprintof each one of the data packets received within the first UDP stream.

In parallel, the second fingerprinter 17 of the STB interface 15 carriesout the fingerprinting process on each UDP packet received within thefirst UDP stream which contains the audio, video and data. Obviously thereceiver module 16, also redirects the first UDP stream to the secondfingerprinter 17 to enable this process.

It should be noted that the fingerprint algorithm implemented by thesecond fingerprinter module 17 is the same as the algorithm implementedat the server side by the fingerprinter module 13, so if both modulesact on the same UDP packet they should obtain the same result, i.e. thesame fingerprint.

By comparing the fingerprinting data received in the second UDP streamand extracted by module 17 with the fingerprinting data calculatedlocally on the first UDP flow, also by module 17, the STB interface 15is able to identify the UDP packets of the first flow (audio, video) tolearn the information associated with these which arrives in the secondflow and is also extracted by module 17.

To summarise, the second fingerprinter 17 receives the second UDP streamwhich contains the fingerprinting data calculated in the firstfingerprinter 13 of the supplier's server 11, and extracts from it theinformation associated with each UDP packet of the first UDP flow.

This associated information is equivalent to that included in otherprotocols such as RTP, and it therefore permits functionalities to beimplemented such as rearrangement of packets, detection of losses,retransmission requests etc in the system described here.

Therefore, in the event that the second fingerprinter module 17 detectsthe absence of a packet, or a packet with errors etc.; the secondfingerprinter 17 or other module may generate a request message whichincludes identification data associated with the erroneous packet.

The aforementioned request is transmitted from the STB interface 15 tothe coder/receiver device 11 so that the packet in question isretransmitted.

As a result of the foregoing, if a legacy STB interface 15 does notinclude the aforementioned second fingerprinter module 17, it willreceive a second UDP stream, however it will be unable to read it andextract the fingerprint information contained in the second UDP streamand it will not be able to carry out functions deriving from thefingerprinting technique, such as additional services of rapid channelswitching, recovery in the event of FEC errors, data synchronised withthe video etc for example.

In any case, the first UDP stream is read by the legacy STB interface15, which has not been altered, and therefore its functioning willcontinue to be the same as prior to the introduction of the second UDPstream.

Consequently, the supplier may deploy and/or gradually update STBinterfaces 15 currently installed, thus permitting some STB interfaces15 to be maintained indefinitely without the new functionalities,without it being necessary to interrupt the service at any time.

In addition, it should be noted that this invention may be implementedby a variety of environments with means which can be read by a computerwhich includes readable codes which can be read by programmablecomputers which include processing components, storage devices from astorage system readable by a computer, which includes memory devices ofa volatile or non volatile memory system.

The logics of both first and second fingerprinters execute various setsof instructions or programmes which are applied to the data packets inorder to carry out the previously described functions.

The programmes used by the hardware modules described above may beimplemented, preferably in various programming languages.

Each computer programme is preferably stored in a module or storagedevice which is readable by a computer programmable for general orspecial use, in order to configure and operate the computer when themodule or storage device is read by the computer in order to execute thepreviously described procedures.

Furthermore, it may be considered that the first and secondfingerprinters may be implemented as a module readable by a computer,configured with a computer programme, which enables the computer tofunction in a previously specified and predefined manner.

The description as explained herein is not considered to be exhaustiveor to restrict the invention to the precise form in which it isdescribed. Modifications and variations are possible in the light of theabove teaching without abandoning the spirit and scope of the followingclaims.

1. Method for ensuring reliability and inserting additional dataassociated to video streams during transmission of the television datastreams from a coding/transmitter device (11) to a group of STB (15)decoder/receiver devices via an Internet protocol telecommunicationsnetwork (14), the method comprising: Generation and transmission from abroadcasting module (12) included in the coder transmitter device (11)of a first UDP data stream to the STB decoder/receiver devices (15),Redirection of the first UDP data stream to a first fingerprint module(13), Reading from the first fingerprint module (13) of the data packetsincluded in the first UDP stream in order to generate and associateidentification data with each packet of the first UDP stream, andGeneration and transmission from the first fingerprint module (13) of asecond UDP data stream relating to the identification data generated tothe STB decoder/receiver devices (15).
 2. Method according to claim 1further comprising: Reception in a receiver module included in the STBreceiver/decoder device (15) from the first UDP data stream and thesecond UDP data stream, Transmission to a second finger print module(17) of the first UDP data stream in order to calculate on the basisthereof, the identification data (fingerprint) on the basis of each UDPpacket in a similar ay as in the first (13) fingerprint module,Transmission of the second fingerprint module (17) of the second UDPdata stream in order to extract it from the identification dataassociated with the packet of the first UDP stream, and Identificationof the UDP packets of the first stream based on the identification dataextracted, to implement in the STB decoder/receiver device (15)functions such as reordering of UDP packets, detection of loss of UDPpackets, request for retransmission of UDP packets.
 3. A first modulereadable by a computer which has instructions readable by computer inorder to give instructions to a computer included in thecoding/transmission device (11) so that the method is executed inaccordance with claim
 1. 4. A second module readable by a computer whichhas instructions readable by computer in order to give instructions to acomputer included in the coding/transmission STB device (15) so that themethod is executed in accordance with claim
 2. 5. An updating method ofan STB receiver/decoder (15) for receiving television data streams froma coding/transmission device (11) via an Internet protocoltelecommunications network (14) comprising installing a secondfingerprinting module (17) electrically connectable to a receiver module(16) of the STB receiver/decoder device so that the receiver (16)retransmits a second UDP stream received by the aforementioned receiverto the second fingerprinter (17) so that it extracts from the second UDPstream identification data associated with packets included in a firstUDP stream also received by the receiver (16).
 6. Updating method inaccordance with claim 5 including, based on the identification dataextracted by the second fingerprinter (17) of the STB receiver/decoderdevice (15), carrying out functionalities such as reordering packets ofthe first UDP stream received, detecting the loss of any packet of thefirst UDP stream received, requesting retransmission of any of the firstUDP stream packets.
 7. Coding/transmission device or transmittingtelevision data streams to a group of STB receiver/decoder devices (15)via an internet protocol telecommunications network (14) comprising afirst fingerprinting module (13) electrically connectable to abroadcasting module (12) of the coder/receiver device (11) so that itreads the first UDP stream in order to generate and associate theidentification of each packet of the first UDP stream.
 8. Device inaccordance with claim 7 wherein the first fingerprinting module (13)generates and transmits a second UDP data stream relating to theidentification data generated, to the STB receiver/decoder devices (15).9. STB receiver/decoder device for receiving television data streamsfrom a coding/transmission device (11) via an internet protocoltelecommunications network (14) comprising a second fingerprintingmodule (17) electrically connectable to a reception module (16) of theSTB decoder/receiver, in such a way that the receiver retransmits thesecond UDP stream received by the aforementioned receiver to the secondfingerprinter in order to extract identification data associated withpackets included in a first UDP stream also received by the receiver(16).
 10. Device in accordance with claim 9 wherein the secondfingerprinter (17) is capable, on the basis of identification dataextracted from the second UDP stream of carrying out functions such asreordering the packets of the first UDP stream received, detecting theloss of any packet of the first UDP stream received, requestingretransmission of any packets of the first UDP stream received.
 11. Amethod for updating a coding/transmission device (11) for transmittingtelevision data streams to a group of STB receiver/decoder devices viaan Internet protocol telecommunications network (14) wherein a firstfingerprinting module (13) is electrically connectable to a broadcastingmodule (12) of the coder/receiver device, so that the firstfingerprinter retransmits a second UDP stream including identificationdata associated with packets included in a first UDP stream transmitted.